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Sunlight's Undeniable Effect on Your Bones

It’s no coincidence that many people feel more energized and motivated when the sun is out. Sunlight can certainly boost our mood, but it actually has more important benefits for our body and mind. One of the main ways our body uses sunlight is to help with the process of building strong bones.

Before we discuss how sunlight helps our bones, we first need to understand how bones are created, since sunlight does not work alone. You may already know that we rely on calcium for bone strength. This is usually because kids are reminded to drink milk to get the calcium they need for strong bones! Although, it’s more accurate to say that our bones are mainly made of calcium along with another mineral called phosphorus. In fact, over 99% of the body’s calcium is found in bone mineral[1]. Since our body cannot create calcium on its own, we rely on food, drink, and supplements to give us the calcium we need.

This is where sunlight enters the picture. The main reason that sunlight helps with bone production is because it provides the body with Vitamin D. This vitamin helps the body better use calcium, which in turn helps form and nourish bones. Sunlight gives us Vitamin D in two ways: our bodies absorb it from the sun that touches our skin and sunlight jump starts the body’s own creation of this vitamin. Unlike calcium, the body can make Vitamin D when it is given the right conditions. It is possible to get some Vitamin D from food and drink, but these sources don’t have nearly as much as the body needs. We rely heavily on sunlight as the main source of this vitamin, since the sun gives us 80 to 90% of our Vitamin D requirements while just 10 to 20% comes from food[2].

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What 10 minutes of sun a day does to your body

While sunlight is what we see and feel, the ultraviolet rays within it are actually what aid in Vitamin D production. Sunlight has two types of ultraviolet rays – ultraviolet A (UVA) and ultraviolet B (UVB). UVB is what the skin needs to create Vitamin D, but both types of ultraviolet rays can be harmful to the body if we do not protect ourselves properly. UVA and UVB rays can both cause sunburn, skin damage, premature aging, and an overall greater risk of skin cancer[3]. This is why skin protection is so important, since experiencing these negative effects can outweigh the benefits of greater Vitamin D production. Sunscreen is one of the most effective ways to protect your face and body from the sun. Regular sunscreen use can reduce someone’s risk of skin cancer between 40 and 50%[4]. Professionals recommend broad spectrum sunscreen, which shields the skin from UVA and UVB damage while still allowing you to take in Vitamin D.

Building bone strength is one of the major ways sunlight helps the body, but Vitamin D has other functions. Most individuals who get very low ultraviolet light exposure and, therefore, have very low Vitamin D levels are at a greater risk of autoimmune conditions[5]. These can include thyroid disorders, diabetes, rheumatoid arthritis, Parkinson’s disease, and multiple sclerosis. While genetics and other factors also contribute to the start of these conditions, it is possible that Vitamin D supplementation can lower someone’s chances of getting an autoimmune condition by up to 22%[6]. This is great for people who cannot get the vitamin naturally from being outside.

Individuals with low levels of Vitamin D are also more likely to experience muscle weakness, low energy, bone fractures, weak teeth, and hair loss. Osteoporosis is one of the most common conditions that is associated with low Vitamin D levels. This condition causes lower bone density, which leads to weaker bones that are more likely to break. Individuals with osteoporosis are known to either not get enough calcium and Vitamin D (either through their diet or outdoor exposure) or their bodies have difficulty properly using what they do have. Research shows that people with osteoporosis who get 5 hours or more of sunlight each day have a significantly lower risk of hip fractures[7].

Whether you have concerns about your Vitamin D levels or are simply looking to get outside more, remember that sun exposure is one of the most available sources of Vitamin D. It’s recommended that people get 10 to 20 minutes of sun on their skin, including the face, arms, and hands, each day[8]. Depending on your skin tone, this is the time it takes for most people to produce Vitamin D. If you have concerns about skin damage and aging, keep in mind that you are more likely to get sunburn when sunlight is more direct between 10 a.m. and 3 p.m.

Anyone looking to increase their Vitamin D intake can also look into Vitamin D3 (also known as cholecalciferol) supplements[9]. This particular type of Vitamin D is the active form, which is more effective since it does not need to be broken down before the body uses it. While this vitamin is available without a prescription, it’s always best to speak with your doctor before taking any new supplements. Your doctor can perform a blood test to determine if your Vitamin D levels are low and offer advice based on the results.

Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Ross, A.C., Taylor, C.L., Yaktine, A.L., et al., editors. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US); 2011. 2, Overview of Calcium. Available from: https://www.ncbi.nlm.nih.gov/books/NBK56060/
Martens, M. C., Emmert, S., & Boeckmann, L. (2020). Sunlight, Vitamin D, and Xeroderma Pigmentosum. Advances in Experimental Medicine and Biology, 1268, 319–331. https://doi.org/10.1007/978-3-030-46227-7_16
D'Orazio, J., Jarrett, S., Amaro-Ortiz, A., & Scott, T. (2013). UV radiation and the skin. International Journal of Molecular Sciences, 14(6), 12222–12248. https://doi.org/10.3390/ijms140612222
The Skin Cancer Foundation. (2022). All About Sunscreen. Retrieved from https://www.skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/
Yang, C. Y., Leung, P. S., Adamopoulos, I. E., & Gershwin, M. E. (2013). The implication of vitamin D and autoimmunity: a comprehensive review. Clinical Reviews in Allergy & Immunology, 45(2), 217–226. https://doi.org/10.1007/s12016-013-8361-3
Bridger, H. (2022). Vitamin D supplements lower risk of autoimmune disease, researchers say. Retrieved from https://news.harvard.edu/gazette/story/2022/01/vitamin-d-reduced-rate-of-autoimmune-diseases-by-22/
Lee, H.J., Kim, C.O., & Lee, D.C. (2021). Association between Daily Sunlight Exposure and Fractures in Older Korean Adults with Osteoporosis: A Nationwide Population-Based Cross-Sectional Study. Yonsei Med J, 62(7):593-599. https://doi.org/10.3349/ymj.2021.62.7.593
International Osteoporosis Foundation. (2023). Vitamin D. Retrieved from https://www.osteoporosis.foundation/patients/prevention/vitamin-d
National Institute of Arthritis and Musculoskeletal and Skin Diseases. (2023). Bone Health and Osteoporosis. Retrieved from https://www.niams.nih.gov/health-topics/bone-health-and-osteoporosis
Last edited on June 1st, 2023 9:19 pm